Craniotomy instrument



March 14, 1967 c. c. PIPPIN 3,308,828

CRANIOTOMY INSTRUMENT Filed Aug. 8, 1965 ALVIN c. P/PP/N INVENTOR.

ATTOQ/VE Y United States Patent f 3,308,828 CRANIOTOMY INSTRUMENT Calvin C. Pippin, Raleigh, N.C., assignor of twenty-eight percent to Eugene E. Bernard, Raleigh, N.C. Filed Aug. 8, 1963, Ser. No. 300,724 Claims. (Cl. 128-310) This invention relates generally to surgical instruments and more particularly to power driven surgical instruments to facilitate the cutting of bone tissue in osteoplastic craniotomies.

Over the years the medical profession has had a problem in cutting various types of relatively hard substances without damaging relatively soft tissues lying thereunder. One of the areas where this problem has arisen is during brain surgery where the skull must be cut and opened and yet the very delicate tissue thereunder must not in any way "be damaged. Another area in which cutting problems has arisen is in removing plaster casts which have been placed on limbs and other parts of the body.

Many years ago in the art of craniotomy a method was developed for opening the osteoplastic flap which consists of passing a protective guide through two previously drilled holes in the skull and then pulling a wire saw through the same, the guide means preventing the brain from being damaged then the saw is manipulated so that the bone between the two drilled holes is cut.

Since this time various instruments, either power driven or hand manipulated such as bone biting forceps, power driven circular saws, dental burr drills, chisels and hammers, various types of hand and power reciprocating saws, ultrasonic Wave and vibrating devices, electric cutting devices and the like have been developed and tested to overcome various inadequacies and also to meet the long felt need for an accurate, easily operated, foolproof type of device for performing the very exacting job of opening the skulls of humans and animals during delicate brain and similar operations.

Even with the various methods and instruments so developed and used, no over-all combination until this time has been found which will meet the very exacting requirements of being fast and eflicient without in any way damaging the tissue being cut so that it will not later properly heal. It has been found that if the instrument moves at too high rate of speed the tissue being cut will become burned, killing it, thereby preventing healing. Further, if the device operates too slowly the surgical operation will be extended a dangerously long period of time and the operation of the device will not be as smooth as possible thereby increasing the possibility of further damage to the delicate underlying tissues.

To overcome these various problems extensive research was done to determine the best method of cutting the skull tissues while doing the least damage thereto. As a result it has been concluded that relatively slow, reciprocatory blade cutting action is the most desirable cutting method. As a further result of said findings the present invention has been developed which will ordinarily operate with a reciprocating motion during the cutting operation but will shift into rotary motion if the saw blade should become bound or clogged so that further reciprocation is difiicult. This automatic conversion from reciprocating to rotary motion tends to clear the clogged blade, thereby allowing it to return of its own accord to its former reciprocating motion thus allowing a fast, accurate and exacting cut to be made in the cranial tissues Without the danger of the blade being put to such stresses that it will snap or break; this of course greatly reduces or eliminates the possibility of patient injury due to surgical instrument malfunction.

3,308,828 Patented Mar. 14, 1967 It is therefore an object of the present invention to provide a relatively low speed saw capable of reciprocative motion connected to a spiral blade which due to the internal structure of the saw will convert from reciprocating to rotary motion, upon theencountering of a resistance to said reciprocating motion.

Another object of the present invention is to provide a surgical instrument for cutting relatively hard material, such as bone, which is powered from a rotary power source and which has a cam shaft connected to said power means at such an angle that a wobble plate connected to said cam will cause the cutting blade to reciprocate when the cam is rotating until some opposing force is applied against the reciprocation wherein the device will convert to rotary motion.

Another object of the present invention is to provide a surgical instrument having a cutting means, a means for converting rotary motion into reciprocating motion to reciprocate said cutting means, a second means to convert said reciprocating means back to rotary motion upon a resistance being applied to the reciprocating movement of said cutting means so that excessive stresses will not be applied to said cutting means and surgical instrument.

Another object of the present invention is to provide a surgical instrument having a drive shaft capable of being rotated, a cam shaft mounted at an angle of approximately 12 degrees to said drive shaft, a wobble. plate mounted about said cam shaft, a connector member connecting said wobble plate to a cutting member in such a manner that when the drive shaft is rotated the cutting member may either rotate, reciprocate or a combination thereof.

Other objects and advantages of the present invention will become apparent and obvious from the study of the following description and the accompanying drawings which are merely illustrative of the present invention.

In the drawings:

FIG. 1 is a sectional view of the instrument of the present invention disclosing the relation of the various parts of such instrument;

FIG. 2 is a sectional view of the lower housing and foot portions of the surgical instrument;

FIG. 3 is an overall exterior view of a preferred embodiment of the present invention; and

FIG. 4 shows the surgical instrument of the present invention as it may be used in opening a portion of the skull.

With further reference to the drawings, FIG. 1 discloses the surgical instrument of the present invention which comprises frustro-conical adapter sleeve 10 having an outwardly flaring collar 11 about its base portion.

A cylindrical or slightly frustro-conical housing 12 is provided which is internally threaded at either end. A shoulder 13 is provided on the interior of the housing 12 at one end thereof.

A cylindrical bearing housing 14 is provided with an outwardly flared collar portion 15 integrally connected thereto. Fixedly connected to the interior of said cylindrical housing 14 is bearing surface 16. Ball bearings 17 are provided between bearing surface 16 and a second bearing surface 18. An enlarged portion 19 is fixedly secured to and internally of said second bearing surface 18.

Drive shaft 20 having enlarged portion 19 at one end thereof is centrally disposed within frustro-conical adaptor sleeve 10. Said drive shaft 20 is rotatably mounted and is connected in any convenient manner to a rotative power source (not shown).

An adaptor sleeve retainer 21 is provided which is externally threaded about its periphery so that such tl reads may co-operatively engage one of the internally threaded end portions of housing 12.

A drive shaft bearing retainer ring 22 is provided which fits within aninternally disposed groove of cylindrical bearing housing 14.

A cam shaft is secured to enlarged portion 19 of drive shaft 20 which consists of an enlarged balancing weight portion 23, an intermediate portion 24, and a Wobble plate axle shaft 25. The center point of the longitudinal axis of the wobble plate axle shaft is in axial alignment with the drive shaft 20 and the spiral cutting blade 39 hereinafter described. Also it has been found that best results are obtained when the longitudinal axes of wobble plate axle and the drive shaft 20 intersect at an angle of approximately 12 degrees.

Mounted about wobble plate axle 25 is bearing surface 26. Ball bearings 27 are provided in operative contactive relation with bearing surface 26 and a second bearing surface 28 and is rotatably mounted about wobble plate axle 25. A shaft 30 is internally mounted through the periphery of said wobble plate 29 in such a manner an enlarged ball or bulbous portion 31 which is integral therewith remains exterior of said wobble plate and adjacent to the periphery thereof.

A connector member composed of a cylindrical portion 32, a frustro-conical portion 33'connected in axial align ment to said cylindrical portion, and a shaft portion 34 connected in axial alignment with said cylindrical and frustro-conical portions is provided. Said cylindrical portion being adapted to be movably mounted within the housing 12. A socket 35 is provided on the interior of said cylindrical portion 32 and is adapted to swivelly engage ball 31.

A funnel shaped lower housing portion 36 having an externally threaded, generally cylindrical lip portion on its larger end is provided. Said exterior threads being adapted to co-operatively engage the interior threads of housing 12 at the end opposite adaptor sleeve retainer 21. The shaft portion 34 of the connector member being adapted to extend through the opening in the lower housing portion 36 when said housing is in threaded connection with housing 12.

A blade receiving well 37 is provided in the shaft portion 34 opposite the frustro-conical portion 33 and in axial alignment with the longitudinal axis of said shaft. A set screw 38 is provided in the side of the shaft portion to retain a spiral or helically shaped cutting blade 39 in fixed position within well 37 of shaft 34.

A guard sleeve 40 is provided which is adapted to slip over the smaller end portion of funnel shaped lower housing 36 and to be fixedly secured thereto by any convenient means such as set screw 41. There is a circular opening 42 in the lower portion of sleeve 40 of such a size that blade 39 may be passed therethrough.

Extending beyond the hole 42 is a leg portion 43 which terminates in an outwardly flared perpendicularly mounted foot portion 44. A recess 45 is provided in said foot portion so'that when blade 39 is reciprocated on its downward stroke it will pass into said recess thereby giving complete cutting action to said blade. It should be noted particularly as shown in FIG. 2 that the thickness of the relatively flat leg portion 43 is less than the slot which will be cut by blade 39.

In actual use of the surgical instrument of the present invention, a hole 47 is drilled through the cranial bone or skull 48 by any convenient means, said hole being of such a size as to receive the foot or shoe portion 44 therein. Care must be taken during drilling and insertion not to rupture the dura mater 49 which acts as a protective covering over the delicate brain tissues. The flared foot portion 44 is placed under the cranial bone between such bone and the dura mater. An upward pressure is maintained to at all times keep the top edge of said foot portion in contactive relation with the underside of said cranial bone.

Shaft 20 is then rotated by any convenient rotative power source (not shown) such as a dental engine, a flexible cable and motor or other means which may be attached within the adaptor sleeve 10 to hold such power means and the surgical instrument in operative connection.

As rotative movement is applied to shaft 20 the cam shaft will rotate while Wobble plate 29 due to the mechanical movement following the course of least resistance, will tend to remain stationary relative to rotary motion thereby causing said plate to wobble or oscillate in such a manner that the ball 31 will reciprocate in a line of travel generally parallel to the longitudinal axis of said drive shaft 20. This oscillating motion is transferred through socket 35 to the connector member and thus to the blade 39 causing such blade to give a cutting action against the bone that it is in contactive relation with.

Teeth 46 may be provided on blade 39 to assist in the cutting process.

As the oscillating blade 39 cuts through the skull, particularly as disclosed in FIG. 4, if due to an accumulation of bone dust tissue or for other reasons such blade becomes bound or for any reason a relatively strong resistance to reciprocating motion is applied thereagainst, the relative movement between wobble plate axle 25 and the wobble plate 29 will cease due to increased resistance thereby causing the connector member including shaft portion 34 to go into rotary motion which in turn causes blade 39 which is fixed thereto to also shift from reciprocating to rotary motion. Such rotary motion will tend to move the clogging or binding material upwardly from the cut slot 50, thereby clearing such obstruction so that when the resistance to reciprocation is sufficiently removed by such rotary motion, the overall device will immediately revert back to reciprocating motion, which has been found to be the best and most advantageous type of cutting motion. .During all of the above described motion shifting or combination thereof, a constant number of revolutions per minute may be maintained on the drive shaft 20 with no disadvantageous results.

It will be obvious that the present invention has the advantage of being relatively inexpensive to manufacture, has few moving parts to wear and has the very distinct advantage of cutting with a reciprocating motion until undesirable obstructions are encountered which place dangerous stresses on the operating device wherein said device automatically shifts from reciprocating to rotary motion or partially shifts to rotary and reciprocating motion until such obstruction is removed by the upward twisting or spiralling action of the cutting means wherein the device will immediately return to such reciprocating motion. Due to the above features the present invention is considered to be economical, safe and a great advancement in a very technical and exacting field.

The present invention of course may be carried out in other specific ways than those herein set forth, without departing from the spirit and essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

What is claimed is:

1. A surgical instrument comprising a drive shaft, means for rotating said drive shaft, a cam means mounted on and at an angle to said shaft, a wobble plate means rotatively mounted on said cam means, connector means, a housing, said connector means slidably and rotatively mounted within said housing in operative relation to said plate means by means of a universal joint and a cutting means fixedly mounted axially on said connector means whereby when said shaft is rotated, said cam will rotate relative to said plate to reciprocate said cutting means axially of the housing until a resistance to reciprocation is applied whereupon said plate will rotate in relative fixed relation to said cam to rotate said cutting means.

2. The device of claim 1 in which the universal joint between said plate and said connector is a ball on the periphery of said plate engaging a socket in said connector whereby reciprocating motion is imparted to the cutting means.

3. The device of claim 1 in which bearing means are provided between said cam and said plate whereby said cam may rotate without causing rotation of said plate.

4. The device of claim 1 in which the angle between said shaft and said cam means is approximately 12 degrees.

5. The device of claim 1 in which the cutting means is a helical blade with a plurality of teeth projecting therefrom.

References Cited by the Examiner UNITED STATES PATENTS 2,105,019 1/1938 Turner 74-6O 2,824,455 2/1958 Ristow et a1. 74-60 2,854,981 10/1958 Morrison 128-317 OTHER REFERENCES Mueller and Company catalog #65, pages 407 and 458.

10 RICHARD A. GAUDET, Primary Examiner.

G. MCNEILL, Assistant Examiner. 

1. A SURGICAL INSTRUMENT COMPRISING A DRIVE SHAFT, MEANS FOR ROTATING SAID DRIVE SHAFT, A CAM MEANS MOUNTED ON AND AT AN ANGLE TO SAID SHAFT, A WOBBLE PLATE MEANS ROTATIVELY MOUNTED ON SAID CAM MEANS, CONNECTOR MEANS, A HOUSING, SAID CONNECTOR MEANS SLIDABLY AND ROTATIVELY MOUNTED WITHIN SAID HOUSING IN OPERATIVE RELATION TO SAID PLATE MEANS BY MEANS OF A UNIVERSAL JOINT AND A CUTTING MEANS FIXEDLY MOUNTED AXIALLY ON SAID CONNECTOR MEANS WHEREBY WHEN SAID SHAFT IS ROTATED, SAID CAM WILL ROTATE RELATIVE TO SAID PLATE TO RECIPROCATE SAID CUTTING MEANS AXIALLY OF THE HOUSING UNTIL A RESISTANCE TO RECIPROCATION IS APPLIED WHEREUPON SAID PLATE WILL ROTATE IN RELATIVE FIXED RELATION TO SAID CAM TO ROTATE SAID CUTTING MEANS. 